Estimating Joule heating and ionic conductivity during flash sintering of 8YSZ

Du, Yaxi; Stevenson, Adam J.; Vernat, Dorothée; Diaz, Magaly; Marinha, Daniel

doi:10.1016/j.jeurceramsoc.2015.10.037

Cited by 77 publications

(60 citation statements)

References 19 publications

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“…Similar conclusions were drawn by Du et al [128] in the case of 8YSZ materials, in their work conductivity of the material in AC was identified as purely ionic. They showed that the extremely high temperature (approaching 1900°C) recorded was sufficient to explain the rapid densification of the material.…”

Section: Proposed Mechanisms In Fssupporting

confidence: 84%

Review of flash sintering: materials, mechanisms and modelling

Grasso

McKinnon

et al. 2016

Advances in Applied Ceramics

401

248

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Flash sintering (FS) is an energy efficient sintering technique involving electrical Joule heating, which allows very rapid densification (<60 s) of particulate materials. Since the first publication on flash-sintered zirconia (3YSZ) in 2010, it has been intensively researched and applied to a wide range of materials. Going back more than a century ago, we have found a close similarity between FS of oxides and Nernst glowers developed in 1897. This review provides a comprehensive overview of FS and is based on a literature survey consisting of 88 papers and seven patents. It correlates processing parameters (i.e. electric field magnitude, current density, waveforms (AC, DC) and frequency, furnace temperature, electrode materials/ configuration, externally applied pressure and sintering atmosphere) with microstructures and densification mechanisms. Theorised mechanisms driving the rapid densification are substantiated by modelling work, advanced in situ analysis techniques and by established theories applied to electric current assisted/activated sintering techniques. The possibility of applying FS to a wider range of materials and its implementation in industrial scale processes are discussed.

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Section: Proposed Mechanisms In Fssupporting

confidence: 84%

Review of flash sintering: materials, mechanisms and modelling

Grasso

McKinnon

et al. 2016

Advances in Applied Ceramics

401

248

View full text Add to dashboard Cite

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“…Wires twisted around each end are used for rectangular bars [46]. The electrodes used for pellets are usually platinum discs placed against the top and bottom surfaces [47] with wires to the power supply attached. Alternative approaches are to attach the wires to meshes of platinum wire placed in the same position as the discs [24], to paint the top and bottom surfaces of the discs with conductive paint/paste (often platinum [48], but silver has also been used [49,50]), or to sputter coat each side of the discs with platinum [51].…”

Section: Electrical Contactmentioning

confidence: 99%

“…Both dogbone shaped samples [4] and pellets [25] have been successfully flash sintered, using both Pt wire electrodes to suspend the dogbones [4,21] and the Pt discs/grids or paint electrodes for pellets [24,25,38,47,78,79].…”

Section: Zirconiamentioning

confidence: 99%

Flash sintering of ceramic materials

Dancer¹

2016

Mater. Res. Express

159

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During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity.Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique nonetheless holds great potential for exceptional control of the ceramic sintering process.

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“…The photoluminescence signals the transition to the nonlinear behavior of the compact's electric conductivity, which otherwise is almost linear with the increase in the temperature [8,9]. Immediate after the flash event, the initial voltage control mode (i.e., constant voltage) exchanged into the current control mode (i.e., constant current) in order to prevent damage of the specimen and the flash sintering system [10,11].…”

Section: Introductionmentioning

confidence: 99%

On thermal runaway and local endothermic/exothermic reactions during flash sintering of ceramic nanoparticles

Chaim

Estournès

2018

J Mater Sci

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OATAO is an open access repository that collects the work of some Toulouse researchers and makes it freely available over the web where possible. ABSTRACTNumerical analysis of the heat balance at the flash event during flash sintering of granular ceramic nanoparticles was performed assuming continuum solid state as well as simultaneous surface softening/liquid formation and current percolation through the nanoparticle contacts. Assuming inter-particle radiations in the specimen volume, the electric Joule heat generated at the nanoparticle contacts partially lost by radiation from the specimen external surfaces. Considering the thermal effects due to rapid heating rate and freemolecular heat conduction regime, high-temperature gradients between the nanoparticle surfaces and the surrounding gas were developed. The attractive capillary forces, induced by the particle surface softening/liquid at the percolation threshold, lead to rapid rearrangement and densification of the nanoparticles. The excess Joule heat, already at the flash event, suffices the excess internal heat that is necessary for partial or full melting. Particle surface softening/liquid formation is a transient process, hence followed by crystallization immediate after the nanoparticle rearrangement. Thermal runaway is associated with local surface softening/melting and its solidification.

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Estimating Joule heating and ionic conductivity during flash sintering of 8YSZ

Cited by 77 publications

References 19 publications

Review of flash sintering: materials, mechanisms and modelling

Review of flash sintering: materials, mechanisms and modelling

Flash sintering of ceramic materials

On thermal runaway and local endothermic/exothermic reactions during flash sintering of ceramic nanoparticles

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